function retTS = price2returnTS(priceTS)
% retTS = price2returnTS(priceTS)  Calculate returns from a price time series
% (retTS = log(price[i]/price[i-1]).  
%

retTS = buildTS(priceTS);
retTS.data(1,:) = 0; % first date gets a return of zero 

retTS.data(2:end,:) = log(priceTS.data(2:end,:)./priceTS.data(1:end-1,:));

return
